It is known to make a freight pallet, that is a rigid load-supporting structure normally having a planar top formed by a single plate or a plurality of coplanar planks and feet formed normally on a plurality of parallel cleats secured underneath the top. Such a pallet is described in French Pat. No. 2,301,441.
In my copending patent application Ser. No. 219,859 filed 23 Dec. 1980 I disclose a method of making a pallet wherein a mass of coarse and fine particles and a binder is filled into an upwardly open elongated mold of generally regular cross section in such a manner that the fine particles are concentrated in the lower portion of the mass and the coarse particles are concentrated in the upper portion of the mass. The mass of particles is then compressed downward in the mold to a relatively great extent at several longitudinally spaced locations and to a lesser extent therebetween to form upwardly projecting bumps between the locations. The thus compressed mass is then cured into a stiffening rib or cleat. At least one board is secured to a plurality of such ribs or cleats arranged parallel to one another.
The pallet according to my earlier invention therefore has at least one board, and a plurality of like elongated stiffening ribs having flat upper sides secured to the board and lower sides formed with downwardly projecting and longitudinally spaced bumps. These ribs or cleats are each formed of a compressed mass of bound-together coarse and fine particles with the coarse particles concentrated toward the respective upper side and the fine particles concentrated toward the respective lower side and bumps. The masses are each compressed more between the bumps than at the bumps.
It is also known, as for example from German patent document 2,508,493 and from U.S. Pat. Nos. 3,104,085 3,342,146, and 4,303,019, to make the entire pallet as a single integral molded element formed of cellulosic, that is plant-origin, particles and an appropriate thermosetting binder. Such pallets are normally relatively weak, being particularly susceptible to damage from bending. It has been suggested in German patent document 3,035,701 to compress the structural members constituting the cleats more between the feet than at them to increase their strength and resistance to breaking in this region. Although an increase in strength is obtained in this manner the resultant pallet is still considerably weaker than a standard solid-oak pallet.